An apparatus for sealing an opening in a metal sheath surrounding an insulated pipe is provided, the apparatus including a base comprising an outer flange securable within the opening, and defining an inner passage therethrough, the base having an annular ridge extending into the inner passage; a flexible waterproof body positionable within the inner passage, the body having a periphery therearound and a groove located within the periphery adapted to engage around the annular ridge; and a flexible metal element within the base.